Node JS null is not an object

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null is not an object (evaluating 'dispatcher.useRef')
useRef@http://localhost:3000/static/js/bundle.js:81360:24
BrowserRouter@http://localhost:3000/static/js/bundle.js:77558:61
renderWithHooks@http://localhost:3000/static/js/bundle.js:25262:31
mountIndeterminateComponent@http://localhost:3000/static/js/bundle.js:29233:32
callCallback@http://localhost:3000/static/js/bundle.js:15518:23
dispatchEvent@[native code]
invokeGuardedCallbackDev@http://localhost:3000/static/js/bundle.js:15562:33
invokeGuardedCallback@http://localhost:3000/static/js/bundle.js:15619:40
beginWork$1@http://localhost:3000/static/js/bundle.js:35517:32
performUnitOfWork@http://localhost:3000/static/js/bundle.js:34765:27
workLoopSync@http://localhost:3000/static/js/bundle.js:34688:26
renderRootSync@http://localhost:3000/static/js/bundle.js:34661:23
performConcurrentWorkOnRoot@http://localhost:3000/static/js/bundle.js:34056:92
workLoop@http://localhost:3000/static/js/bundle.js:42096:46
flushWork@http://localhost:3000/static/js/bundle.js:42074:26
performWorkUntilDeadline@http://localhost:3000/static/js/bundle.js:42311:46

`
import React, { useEffect, useState } from 'react'
import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';

import "./App.css";

import "bootstrap/dist/css/bootstrap.min.css"
import "bootstrap/dist/js/bootstrap.min.js"
import { Header } from "./components/layout/Header";
import { Footer } from "./components/layout/Footer";
import { Home } from './components/Home';

function App() {
const [message, setMessage] = useState("");

useEffect(() => {
  fetch("http://localhost:8000/message")
    .then((res) => res.json())
    .then((data) => setMessage(data.message));
}, []);

return (
  <Router>
    <div className="App">
    <>
      <Header> 
        <Route path="/" component={Home} exact />
      </Header>
      <Footer></Footer>
    </>
  </div>

  </Router>
);

}

export default App
`